Mechanisms of action studies will be carried out on anticancer drugs which have shown potential in clinical trials or which are undergoing or about to undergo clinical trials. These mechanisms of action studies will be directed at the molecular level and specifically to enzymes which are inhibited by the compounds. A portion of our effort will also be directed to studies in depth of several potential anticancer agents that we have designed and synthesized. Specifically, these are compounds which have the potentiality of circumventing drug resistance due to "deletions" of nucleoside kinases and drug resistance due to high tumor or tissue levels of the nucleoside deaminases, adenosine and cytidine deaminases.